Wednesday, May 04, 2016

Physiology in action - water loss on low carb diets

I liked the days when diets were supposed to be low in fat, and even low in protein. (For every appetite there is a historic “best diet” recommendation.)

Alas, carbs are somewhat out of fashion these day [1]. So when I am home, and being good, I control carbs. I also do a relatively extreme amount of exercise. When I am away I sin with carbs and exercise less — and my weight jumps 3-5 lbs very quickly. [2]. When I reform I “diurese”, which is a medically polite way of saying I pee a lot and drop the weight.

…low-carbohydrate diets also initially induce significant water diuresis. The majority of this diuresis is likely the result of glycogenolysis from increased protein consumption. Glycogen binds water at a rate of 2 to 4 g of water per gram of glycogen. As glycogen stores are consumed for energy, two to four times that weight in water is shed through urine. Thus, a portion of the early weight loss in these diets is water weight.

I think my body is “good” at building glycogen stores, and not bad at using them when I reform.

[2] I’m being circumspect, because I think my weight makes these sudden jumps after I quit sinning, decrease carbs, and increase exercise. If this impression is correct I might hypothesize that my body responds to the double hit of more exercise and fewer carbs by stuffing what carbs and fat I get into water rich stores. These then have to be depleted.